Postscript announced it has raised $4.5 million in seed funding to help bring turbocharged SMS marketing to Shopify and e-commerce stores.

Postscript specializes in SMS marketing for e-commerce. The company’s goal is to help bring SMS marketing mainstream, while at the same time doing it in a way that respects users’ inboxes.

The company has now raised $4.5 million to help it reach that goal. The investors include Y Combinator, Accomplice, 1984vc, and Ali Capital. Postscript also has the backing of some of the biggest entrepreneurial names in the e-commerce industry.

“At Postscript, we obsess about supporting independent brands & e-commerce merchants and will always put their needs first,” said CEO Adam Turner. “Our approach to text messaging emphasizes brands build meaningful relationships with their customers by respecting the SMS inbox and encouraging two way communication. So far our competitive advantage has been our people and our product, and this funding will help us continue along that path. By operating remotely, we’re able to hire in any region, resulting in an extremely talented team dedicated to delivering a top-tier product and customer experience.”

Postscript already claims Native, Brooklinen, StackCommerce, Frey, Oars + Alps and Olivers among its clients. The company also boasts 26x ROI with clickthrough rates ranging between 7.5% and 40%. Somewhat unique to the industry, Postscript guarantees a 4x ROI or they will refund a client’s investment — something they have not yet had to do.

“The Postscript team has taken a product-first approach to a gigantic, fast-growing market, and the growth speaks for itself,” said angel investor Paul English, founder of Kayak. “They have outstanding founder/product/market fit, and I believe what they’re building will be an essential part of any e-commerce company’s marketing stack. I’m proud to support them in this round.”